In a mobile communication system, there is a known method for forming communication areas using a plurality of cells that use the same frequency in order to effectively use limited frequencies. LTE (Long Term Evolution) by 3GPP (3rd Generation Partnership Project) disclosed in Non Patent Literature 1 and the like employ this method.
On the other hand, with a cell configuration where the same frequency is used for a plurality of cells, there is large interference from an adjacent cell in a boundary region between the cells. Therefore, quality of reception signals in a radio terminal remarkably deteriorates. In particular, reception signal quality of a static terminal and a low-speed mobile terminal may be stationary or becomes low for a long time. A method for restricting resource allocation in adjacent cells has been investigated as a method for reducing such interference between cells. Hereinafter, an inter-cell interference reduction method disclosed in Patent Literature 1 will be explained.
As shown in FIG. 20, a radio station 200 sends a request for reducing interference on a resource which will be used to a radio station 210 that is an interfering source on the radio resource which will be used. The radio station 210 which has received the request for reducing the interference restricts usage of the radio resource at the same time and in the same frequency in order to reduce the interference on the corresponding radio resource. By doing so, the interference on a radio terminal 220 from the radio station 210 in the boundary region between the cells can be reduced.